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PTY(4) FreeBSD Kernel Interfaces Manual PTY(4)
NAMEpty -- BSD-style and System V-style compatibility pseudo-terminal driver
SYNOPSISdeviceptyDESCRIPTION
The pty driver provides support for the traditional BSD naming scheme
that was used for accessing pseudo-terminals. When the device /dev/ptyXX
is being opened, a new terminal shall be created with the pts(4) driver.
A device node for this terminal shall be created, which has the name
/dev/ttyXX.
The pty driver also provides a cloning System V /dev/ptmx device.
New code should not try to allocate pseudo-terminals using this inter-
face. It is only provided for compatibility with older C libraries that
tried to open such devices when posix_openpt(2) was being called.
FILES
The BSD-style compatibility pseudo-terminal driver uses the following
device names:
/dev/pty[l-sL-S][0-9a-v] Pseudo-terminal master devices.
/dev/tty[l-sL-S][0-9a-v] Pseudo-terminal slave devices.
/dev/ptmx Control device, returns a file descriptor to a
new master pseudo-terminal when opened.
DIAGNOSTICS
None.
SEE ALSOposix_openpt(2), pts(4), tty(4)HISTORY
A pseudo-terminal driver appeared in 4.2BSD.
BUGS
Unlike previous implementations, the master and slave device nodes are
destroyed when the PTY becomes unused. A call to stat(2) on a nonexis-
tent master device will already cause a new master device node to be cre-
ated. The master device can only be destroyed by opening and closing it.
The pty driver cannot be unloaded, because it cannot determine if it is
being used.
FreeBSD 10.1 August 20, 2008 FreeBSD 10.1